The present invention relates to a highly crater-resistant, high-strength sintered material and sintered body. Particularly, it relates to a high pressure phase-type boron nitride-based sintered material for cutting tools, having improved wear resistance and toughness.
A high pressure phase-type boron material, a typical example of which is cubic boron nitride (hereafter referred to as xe2x80x9ccBNxe2x80x9d), is a highly hard substance next to diamond in hardness. A cBN-based sintered material is used for various cutting tools, wear-resistant parts, impact-resistant parts and the like.
In this type of the sintered material, the compatibility between hardness and strength is difficult. As techniques aiming at this compatibility, mentioned are, for example, JP-B-62-25630, JP-B-62-25631 and JP-A-05-186272. These documents describe that the sintered materials disclosed are excellent in failure resistance and exhibit excellent performances in interrupted cutting of hardened steel, and that the cutting conditions are so limited that the cutting speed V is at most about 100 m/min.
If the above-mentioned sintered materials are used under the conditions that the temperature of the cutting edge is high and the impact is large, as in high-speed interrupted cutting of hardened steel at a cutting speed V of at least 150 m/min, the development of crater wear and the generation of cracks at a crater portion are observed, resulting in a failure with a short tool life.
Accordingly, a main object of the present invention is to provide a sintered material which is excellent in crater resistance and exhibits a long tool life even under such conditions that the temperature of the cutting edge becomes high and the impact is large, as in high-speed interrupted cutting of hardened steel.
The highly crater-resistant, high strength sintered material according to the present invention is a highly crater-resistant high-strength sintered material comprising high-pressure phase-type boron nitride and a binder. The high-pressure phase-type boron nitride is contained in an amount of from 50% to 78% by volume based on the sintered material, and the balance comprises a binder phase. The binder phase comprises at least one selected from the group consisting of nitrides, carbides, carbonitrides and borides of Ti, nitrides, borides and oxides of Al, carbides and borides of W, nitrides, carbides, carbonitrides and borides of Co, and carbides and borides of Ni, and/or mutual solid solutions thereof. The binder phase is continuous in a sintered material texture. The amount of the metal components Al, W, Co and Ni which exist as the compounds in the sintered material are from 3 to 20% by weight based on the sintered material. These compounds constitute the binder phase. The sintered material according to the present invention, of course, may contain unavoidable impurities.